The present invention relates to a camera provided with an automatic focusing system and, more particularly, to a power supplying system employed in a camera for supplying the electric power to the automatic focusing system.
When taking a photograph with the above described type of camera, it is necessary for the automatic focusing system to determine the distance between the camera and a target object before releasing the shutter mechanism. For this reason, it is preferable to render the automatic focusing system operative before the release of the shutter mechanism. In this sense, it is quite difficult to control the supply of power to the automatic focusing system.
Generally, the automatic focusing system includes a distance measuring element which consumes a very large amount of electric power during its operation. Therefore, it is practical to operate the automatic focusing system for as short a period of time as possible before releasing the shutter mechanism.
In order to meet this requirement, the automatic focusing system may be made operative simultaneously with the start of movement of depression of the shutter button. However, since the automatic focusing system includes a capacitive component, the time interval between the start of movement of the shutter button and the termination of this movement, which coincides with the moment when the shutter mechanism is released, is typically not enough for the capacitive component to be charged with a sufficient voltage. In other words, the automatic-focusing system requires a longer period of time than this time interval to establish a stable operating condition. Furthermore, it is necessary to provide the necessary time to shift the objective lens assembly of the camera in accordance with a measured signal obtained from the automatic focusing system before releasing the shutter mechanism after the measured signal is obtained from the automatic focusing system in a stable condition. Therefore, in order to provide sufficient time for the automatic focusing system to establish a stable operating condition and for the objective lens assembly to be placed in a properly focused position in accordance with the received measured signal, it is necessary to supply electric power to the automatic focusing system before the start of movement of the shutter button.
Although this requirement may be met by providing a manually operable switch to the automatic focusing system, the photographer may often forget to turn such a manually operable switch on or off.